Fix crash in notifyTwitchChannelOffline when snapshot is empty (#6604)

Reviewed-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

CHANGELOG.md

@@ -51,7 +51,7 @@
 - Dev: Mock headers are now added as a header set if supported by CMake. (#6561)
 - Dev: Set settings directory to temporary one used in tests. (#6584)
 - Dev: Check Lua unwinding and version in tests. (#6586)
-- Dev: Added method to get the last N messages of a channel. (#6602)
+- Dev: Added method to get the last N messages of a channel. (#6602, #6604)
 
 ## 2.5.4
 

src/controllers/notifications/NotificationController.cpp

@@ -156,6 +156,13 @@ void NotificationController::notifyTwitchChannelOffline(const QString &id) const
     // "delete" old 'CHANNEL is live' message
     const LimitedQueueSnapshot<MessagePtr> snapshot =
         getApp()->getTwitch()->getLiveChannel()->getMessageSnapshot(200);
+
+    // Guard against empty snapshot to prevent underflow and invalid access
+    if (snapshot.size() == 0)
+    {
+        return;
+    }
+
     for (size_t i = snapshot.size() - 1; i >= 0; --i)
     {
         const auto &s = snapshot[i];